1. Field of the General Inventive Concept
The present general inventive concept relates to a developing device including a developing roller that supplies a toner to a photosensitive member to develop an image and an electrophotographic image forming apparatus adopting the developing device.
2. Description of the Related Art
An electrophotographic image forming apparatus prints images on a recording medium by forming an electrostatic latent image on a surface of a photosensitive member by irradiating a light beam that is modulated according to image information onto the photosensitive member, developing the electrostatic latent image into a visible toner image by supplying a toner onto the electrostatic latent image, and transferring the toner image onto the recording medium to fuse the toner image. The electrophotographic image forming apparatus includes a developing device in which the toner is received.
The toner may be provided as a cartridge including a developing roller, and the cartridge may be referred to as a developing device. When the toner received in the developing device is completely consumed, the developing device is extracted from the image forming apparatus, and a new developing device is mounted in the electrophotographic image forming apparatus.
The developing roller contacts the photosensitive member to have a predetermined nip therebetween, or may be disposed separate from the photosensitive member such that there is a developing gap between the developing roller and the photosensitive member. For a high quality print image without defects, such as a missing or misplaced image, the nip or the developing gap has to be maintained constant. To do this, the developing roller is pressed towards the photosensitive member. If the pressing force is too small, defects, such as the missing or misplaced image, may occur, and if the pressing force is too large, the photosensitive member may be damaged and a driving load of the developing device is increased.